In recent years, new electronic devices to meet the market trends that have tended to be lighter in weight, thinner, shorter, smaller, and better performing than previous generations. Packages with small size are critical to the packaging industry. The wafer level chip scale package (WLCSP) is leading a trend for use in portable computers, mobile devices (e.g. tablet computer and the like), information and communications technology (ICT) products, automobiles, and wearable products. The 3D IC package has been developed gradually in the semiconductor industry due to marketing and the requirements on product functionality. The conventional flip chip reflux bonding has been replaced with hot-pressing bonding, in which the technique of hot pressing a non-conductive paste also developed quickly in recent years.
The properties required of a suitable thin film packaging material for the WLCSP include excellent adhesion between a B-stage film and the chip, transparency of the B-stage film for alignment, and low stress. In addition, the B-stage film that adheres to the wafer may sustain cuts. The epoxy resin, which used widely in regular semiconductor device packaging and printed circuit board manufacturing, has characteristics of processability, high thermal resistance, and high humidity resistance, but cannot satisfy the high reliability requirement in semiconductor device packaging. Accordingly, a packaging material with properties suitable for the WLCSP is called for.